Bottle Closure Sealing SystemBottle Closure Sealing System

Mark NaumanMark Nauman

Andrew SeagravesAndrew Seagraves

Jeff StaniszewskiJeff Staniszewski

Vincent UathavikulVincent Uathavikul

Design ReportDesign Report

BackgroundBackground

• Berry Plastics Berry Plastics - New child resistant timed-closure New child resistant timed-closure

developeddeveloped- Cap intended to seal without a linerCap intended to seal without a liner

• Dome designed to flexDome designed to flex

• Initial FEA Initial FEA - Cap showed plastic deformationCap showed plastic deformation- Inadequate for sealing as isInadequate for sealing as is

Problem DefinitionProblem Definition

• To design a liner for their existing closureTo design a liner for their existing closure

ConstraintsConstraints• Process: Compression MoldingProcess: Compression Molding• Material: Thermoplastic Elastomer (TPE)Material: Thermoplastic Elastomer (TPE)

System Level WantsSystem Level Wants• Create a seal for a liquidCreate a seal for a liquid• Maintain seal for 1 yearMaintain seal for 1 year• Minimize cost per unitMinimize cost per unit• Achieve seal within tolerance rangeAchieve seal within tolerance range

Project ScopeProject Scope

• Project WantsProject Wants• Create a waterproof sealCreate a waterproof seal

- in a leak testin a leak test- in an accelerated creep testin an accelerated creep test

• At nominal dimensionsAt nominal dimensions

• Within tolerance rangeWithin tolerance range

• Minimize cost per unit byMinimize cost per unit by- Minimizing material costsMinimizing material costs- Minimizing tooling costsMinimizing tooling costs

• Project MetricsProject Metrics• Performance in aPerformance in a

- standard leak teststandard leak test- elevated temperature leak elevated temperature leak

testtest• Nominal bottles and capsNominal bottles and caps

• Max bottle with min capMax bottle with min cap

• Min bottle with max capMin bottle with max cap

• VolumeVolume• Machining time of toolingMachining time of tooling

TerminologyTerminology

Compression MoldingCompression Molding

Initial ConceptsInitial Concepts

Constant Thickness

Variable Thickness

Cutaway Concept

Comparative Leak TestComparative Leak Test

PurposePurpose• Compares the sealing performance of Compares the sealing performance of

Constant and Variable conceptsConstant and Variable concepts

SpecificsSpecifics• 6 Different Torques6 Different Torques

- From 2 to 12 inch-poundsFrom 2 to 12 inch-pounds- 3 samples per torque level3 samples per torque level- Constant volume of water + food coloringConstant volume of water + food coloring

ResultsResults• No leaks with any sample after 48 hoursNo leaks with any sample after 48 hours

ConclusionsConclusions• Constant and Variable are equivalent in sealingConstant and Variable are equivalent in sealing

Comparative Cost StudyComparative Cost Study

At 50 million units…At 50 million units…

Cost / Unit Cost / Unit Total Cost of Total Cost of ProductionProduction

CutawayCutaway $0.0114$0.0114 $570,000$570,000

ConstantConstant $0.0126$0.0126 $630,000$630,000

VariableVariable $0.0118$0.0118 $590,000$590,000

AssumptionsAssumptions• Production: 50 Million parts/yrProduction: 50 Million parts/yr• TPE bulk cost: $2 / poundTPE bulk cost: $2 / pound• Cost of Machining Punches: Cost of Machining Punches:

$70/hr$70/hr

ResultsResults• Constant concept costs Constant concept costs

- 9.5% more than the Cutaway9.5% more than the Cutaway- 6.3% more than the Variable6.3% more than the Variable

• At 50 million parts, material At 50 million parts, material costs account for ~ 16% of the costs account for ~ 16% of the total costs and 50% of the total costs and 50% of the controllable costscontrollable costs

Cost per Unit vs. # of Units

0.0010

0.0100

0.1000

1.00E+07 1.00E+08 1.00E+09 1.00E+10

# of UnitsC

ost

Per

Un

it

Constant

Variable

Cutaway

Manufacturing ConcernsManufacturing Concerns

• Easier to seal off in Easier to seal off in the land area instead the land area instead of ridgeof ridge

• Variable and Cutaway Variable and Cutaway concepts now virtually concepts now virtually the samethe same

Cap Sleeve Punch

Ridge Liner

Concept EliminationConcept Elimination

• Constant and Variable liners have the Constant and Variable liners have the same sealing performancesame sealing performance

• Variable liner will cost less than ConstantVariable liner will cost less than Constant

• Cutaway and Variable are the same Cutaway and Variable are the same because of manufacturingbecause of manufacturing

Variable Concept willVariable Concept will

be prototypedbe prototyped

Simple ModelSimple ModelCap Liner

Bottle

Select Section View

Instron TestingInstron TestingTorque to Pressure Data

0

10

20

30

40

50

60

1 2 3 4 5 6

Torque (in-lb)

Pre

ssu

re (

psi

) Measured Values

Best Fit Line

• Linear Correlation found between Torque Linear Correlation found between Torque and Pressure can be used for FEA and and Pressure can be used for FEA and also by Berry Plasticsalso by Berry Plastics

Finite Element AnalysisFinite Element Analysis• Model of Cap, Liner and BottleModel of Cap, Liner and Bottle

• Force applied to contact areaForce applied to contact area• Boundary ConditionsBoundary Conditions - Cap sides are stationary- Cap sides are stationary - Bottle can move in y-direction- Bottle can move in y-direction

Finite Element Analysis ResultsFinite Element Analysis Results

• A cap with no liner contained stresses above yield limitA cap with no liner contained stresses above yield limit• A cap with a liner was close to yield limitA cap with a liner was close to yield limit

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

7 8 9 10 11 12 13 14

Closing Torque (in lb)

Stress (psi) -

Max SeqvMax SxMax SyFlexural Limit

Validation of Test DesignValidation of Test Design• O-ring and compression liners compared O-ring and compression liners compared

with FEAwith FEA

• O-ring liner performs similar to actual O-ring liner performs similar to actual design under same loaddesign under same load- Within 8% on all stressesWithin 8% on all stresses- Within 2% on all deflectionsWithin 2% on all deflections

• O-ring is an accurate O-ring is an accurate approximation geometryapproximation geometry

Standard Leak TestStandard Leak TestProcedureProcedure• Bottles are sealed to predetermined range of torqueBottles are sealed to predetermined range of torque• Opening torque immediately applied and measuredOpening torque immediately applied and measured• Bottles are resealed and checked for leaking over 2 Bottles are resealed and checked for leaking over 2

week timeweek time• Opening torque is applied and measuredOpening torque is applied and measured

ResultsResults• No bottles leak in this timeNo bottles leak in this time• Opening torque slightly lower Opening torque slightly lower

after 2 weeksafter 2 weeks

Douter = 1.42”Dinner = 1.06”Thickness = .04”

Elevated Temperature TestElevated Temperature Test

• Used to simulate relaxation over timeUsed to simulate relaxation over time• Sealed bottles are put in environmental chamberSealed bottles are put in environmental chamber

- 2 weeks at 100 2 weeks at 100 °F ~ 2 months°F ~ 2 months

• All bottles remained sealed over periodAll bottles remained sealed over period• Relaxation curve made using existing dataRelaxation curve made using existing data

- Immediate opening torqueImmediate opening torque- Opening torque after 2 weeksOpening torque after 2 weeks- Opening torque after simulated 2 monthsOpening torque after simulated 2 months- Match shape of current relaxation curvesMatch shape of current relaxation curves

Elevated Temperature Test ResultsElevated Temperature Test Results

• 10 in lb may be 10 in lb may be inadequate to sealinadequate to seal- Cap relaxes too Cap relaxes too

much over the periodmuch over the period

• Higher than 12 in lb Higher than 12 in lb will seal over timewill seal over time- Curves flatten outCurves flatten out

ConclusionsConclusions• Testing ShowsTesting Shows

- Prototype maintains short term waterproof sealPrototype maintains short term waterproof seal• Performance Metric of Standard Leak test satisfiedPerformance Metric of Standard Leak test satisfied

- Waterproof seal intact after simulated 2 monthsWaterproof seal intact after simulated 2 months• Performance Metric of Elevated Temperature test satisfiedPerformance Metric of Elevated Temperature test satisfied

• FEA ShowsFEA Shows- Prototype design and actual design behave similarPrototype design and actual design behave similar- Higher torques could cause plastic deformationHigher torques could cause plastic deformation

• Analysis ShowsAnalysis Shows- Seal would survive simulated yearSeal would survive simulated year

• PrototypePrototype- Simulates the actual liner design to be implemented by BerrySimulates the actual liner design to be implemented by Berry

Implementation PlanImplementation Plan

• Test the cap for relaxation over a Test the cap for relaxation over a simulated yearsimulated year

• Optimize liner thickness to Optimize liner thickness to reduce production costsreduce production costs

• Small scale production of punch Small scale production of punch for further physical and for further physical and consumer testingconsumer testing

• Large scale production of punch Large scale production of punch for commercial use of cap and for commercial use of cap and linerliner

QuestionsQuestions

• Elevated Temperature

• FEA Stress

• Manufacturing

• Simple Model

• Instron Setup

• Tolerance Variation